リテラル (Ruby 3.3 リファレンスマニュアル)
* [[ref:num]] * [[ref:string]] * [[ref:backslash]] * [[ref:exp]] * [[ref:char]] * [[ref:command]] * [[ref:here]] * [[ref:regexp]] * [[ref:array]] * [[ref:hash]] * [[ref:range]] * [[ref:symbol]] * [[ref:percent]]